The present invention relates to manufacturing methods of photomasks, methods for optical proximity correction, and manufacturing methods of semiconductor devices and in particular to a manufacturing method of a photomask for forming hole features and line features, a method for optical proximity correction used to manufacture such a photomask, and a manufacturing method of a semiconductor device using this photomask.
In the manufacture of a semiconductor device, a semiconductor element, a wiring, or the like is formed by repeating the following steps: a step of forming a predetermined film, such as an insulating film or a conductive film, over a semiconductor substrate, a step of carrying out processing, such as etching, on the film, and the other like steps. Before this processing is carried out, a resist pattern is formed over a predetermined film by a lithography process. In the lithography process, it is important to form a desired resist pattern so that desired pattern dimensions and shape can be obtained by processing such as etching.
In conjunction with the microminiaturization of patterns, there is a tendency of the shape or dimensions of a resist pattern to deviate from the shape or dimensions of the pattern with designed values. When a photomask is manufactured, for this reason, processing is carried out to correct the data of the pattern of the photomask to make a resist pattern actually formed over a semiconductor substrate agree with a desired finished shape. This processing is designated as optical proximity correction (OPC).
A photomask pattern is determined based on data corrected by this optical proximity correction and there are model-based OPC and rule-based OPC as techniques therefor. In model-based OPC, a photomask pattern is determined by taking the following procedure: a design pattern is divided into small sides; each side is corrected by optical proximity correction built based on experimental values; an actually delineated resist pattern is estimated by shape simulation using the corrected pattern; and pattern deformation and shape simulation for the resist pattern are repeated until a desired resist pattern is obtained. In rule-based OPC, meanwhile, a photomask pattern is determined by correcting pattern data with designed values with a preset amount of correction for optical proximity correction.
A photomask is manufactured based on data of a photomask pattern finally determined as mentioned above. First, a resist film for electron beam exposure over a light shield film formed over the surface of a glass plate is scanned with an electron beam based on the data and a layout pattern is thereby drawn. Subsequently, the resist film for electron beam exposure is subjected to predetermined development and a resist pattern corresponding to the layout pattern is thereby formed. Subsequently, the light shield film is subjected to etching using the resist pattern as a mask and a photomask is thereby formed.